A study on the influence of liquid water and water vapour on the self-ignition of lignite coal-experiments and numerical simulations

Experiments were carried out for German lignite coal sampled in two different particle size fractions. They showed, that subcritical deposits turned to supercritical behaviour if the relative humidity in the surrounding was suddenly increased or water was poured on the surface of the sample. Besides the experiments, a numerical model was established to describe the effects of self-heating until ignition of the deposit, including the transportation of moisture. Simulations with this model led to satisfying results when compared to the experiments.